Random Copolymers Of Acrylamide Research Articles

Effect of pH on the Behavior of a Random Copolymer of Acrylamide

A temperature- and pH-sensitive random copolymer of N-[3-(diethylamino)propyl]-N-methylacrylamide] and N,N-diethylacrylamide was obtained. The copolymer contained 20 mol % of amine units and had a molecular weight of 3.3 × 104. Buffer solutions containing 0.0102 g/cm3 of the synthesized copolymer were studied in the pH range of 7–13.5 by light scattering and turbidimetry. At low temperatures, macromolecules and large aggregates coexist in the solutions. The copolymer is temperature- and pH-sensitive in the studied pH range. The temperature and the width of the phase separation interval increase with increasing acidity of the medium.

Ultrasensitive pH-Induced Water Solubility Switch Using UCST Polymers

For some thermosensitive polymers, the absence of an upper critical solution temperature (UCST) in water in an accessible temperature range (say, 5–90 °C) can be attributed to the influence of charged groups in the polymer structure. This property was exploited in the present study to achieve ultrasensitive pH-induced water solubility switch of UCST polymers in physiological medium. By incorporating either acrylic acid (AAc) or 4-vinylpyridine (4VP) comonomer units in the random copolymer of acrylamide and acrylonitrile (P(AAm-co-AN-co-AAc) or P(AAm-co-AN-co-4VP)), the pH-induced shift of UCST was investigated by monitoring the solution cloud point. The results revealed an unusually large shift of the cloud point upon pH variation over a small range. In particular, one P(AAm-co-AN-co-4VP) sample exhibited a cloud point drop from 72 °C at pH 4.75 to 15 °C at pH 4.50 (i.e., 57 K shift over 0.25 pH units), and its transition from soluble to insoluble state at room temperature was visually observable over a p...

Features of the foaming of acrylamide-acrylic acid copolymers

The processes that occur during the processing and foaming of thermosetting composites based on a random copolymer of acrylamide and acrylic acid—softening, foaming, and curing of the copolymer—are studied with the use of methods of chemical kinetics, Fourier transform infrared spectroscopy, and thermomechanical analysis. The above processes are coordinated with respect to time and temperature; prognostic methods for calculating the dynamics of these processes and the properties of foam materials as functions of the composition of the original foam-forming composite and the foaming conditions are proposed.

Comb-like thermoresponsive polymeric materials: Synthesis and effect of macromolecular structure on solution properties

A series of comb-like block and random copolymers based on acrylamide (AM) and N-isopropylacrylamide (NIPAM) have been prepared by atom transfer radical polymerization (ATRP). The number of side-arms, the length of the AM and NIPAM blocks as well as the distribution of the two monomers (block or random) were systematically varied. The aqueous solution properties, i.e. the solution viscosity as a function of shear rate and temperature and the critical micelle concentration (CMC) of the different copolymers were evaluated. Particular emphasis is dedicated to the thermo-responsiveness of the aqueous copolymer solutions as measured by the rheological behaviour. The CMC is a function of the molar ratio between the AM and NIPAM, as well as the distribution (block or random). The surface tension of the block copolymers is close to the value for pure poly(NIPAM), while that of the random copolymers is a function of the composition. The block copolymers tend to precipitate from the solution at temperatures above the Lower Critical Solution Temperature (LCST) of poly(NIPAM), indicating the formation of strong aggregates. Random copolymers of AM and NIPAM do not precipitate from the solution (up to 80 °C). In addition, depending on the composition, thermothickening behaviour is observed. The thermothickening behaviour is only present at low shear rates (γ ≤ 10 s−1). This, in connection with the ease of the synthesis, makes these copolymers especially interesting for application in Enhanced Oil Recovery (EOR).

Electrophoretic analysis of cations using large-volume sample stacking with an electroosmotic flow pump using capillaries coated with neutral and cationic polymers

To realize the high-performance and simple-operation analysis of cationic compounds in capillary electrophoresis, we investigated large-volume sample stacking with an electroosmotic flow pump (LVSEP) using capillaries with hydrophilic and weakly cationic inner surface. Three capillary modification methods were employed: thermally passivated physical coating with polymer mixture of poly(vinyl alcohol) and poly(allylamine); covalent modification with random copolymer of acryl amide and 3-(methacryloylamino)propyltrimethylammonium chloride; easily preparable physical coating with dimethyldioctadecylammonium bromide and polyoxyethylene stearate. In these capillaries, the electroosmotic flow (EOF) was well suppressed in the high ionic strength (I) electrolyte under the acidic and basic pH, whereas the EOF was enhanced in the low I electrolyte, indicating a suitable EOF property for the rapid LVSEP and following separation. In the LVSEP-capillary zone electrophoresis (CZE) analyses of benzylamine and 1-naphthylethylamine, up to 550-fold sensitivity increases were successfully obtained in the three capillaries without significantly reducing the repeatability and resolution. LVSEP-cyclodextrin-modified CZE of chlorpheniramine and brompheniramine was also carried out, resulting in up to 380-fold sensitivity enhancement with keeping the baseline separation for the enantiomers. Finally, we performed the LVSEP-CZE analysis of basic proteins, where up to 100-fold sensitivity increases were achieved, but a peak broadening was observed due to the sample adsorption in the low I sample matrix.

Swelling and mechanical behavior of ionized poly(acrylamide-co-N,N’-diethylacrylamide) gels in water/acetone mixtures and in water at various temperatures

Ionized networks of random copolymers of acrylamide (AAm) and N,N’-diethylacrylamide (DEAAm) (mole ratios of xAAm/xDEAAm=1/0,0.75/0.25,0.5/0.5,0.30/70,0.15/0.85,0/1) with various amounts of ionic comonomer-sodium methacrylate (MNa) (mole ratios to all monomers xMNa=0.0,0.025,0.05) and crosslinker – N,N’-methylenbisacrylamide (MBAAm) were prepared at high dilution in water. Their swelling and mechanical behavior was investigated in water at various temperatures (from 10 to 90 °C) and in water/acetone (w/a) mixtures at room temperature. For some copolymers the transition region from expanded to collapsed state was observed at critical concentration of acetone, ac, in w/a mixtures or at critical temperature, Tc, in water. It was found that with increasing content of DEAAm component in copolymers the ac values increase; the similar increase was observed with increasing xMNa. Neat PDEAAm and copolymers with the highest DEAAm content exhibit temperature transition; both increasing amount of AAm and charges bound on the chains (xMNa) in copolymers shifts the Tc temperatures to higher values very efficiently (for more than 20 °C).

Influence of Concentration and Molecular Characteristics of Copolymers of Acrylamide with Sodium Acrylate on the Thoms Effect in Oil-in-Water Emulsions

The effect of the concentration and molecular parameters of random copolymers of acrylamide and sodium acrylate on their performance as additives reducing the hydraulic resistance of turbulent flows in oil-in-water emulsions is quantitatively studied.

Sedimentation Kinetics of Bentonitic Clay Suspension as Influenced by pH of the Medium, Chemical Nature and Concentration of Surfactants, and Molecular Properties of Cationic Acrylamide Copolymer Flocculants

The kinetics of flocculation of bentonitic clay suspensions and thickening of the sediments was studied in the modes of free and hindered sedimentation as influenced by pH of the medium, chemical nature and concentration of surfactants, and molecular properties of cationic flocculants, random copolymers of acrylamide with dimethylaminoethyl methacrylate hydrochloride.

Weakly Charged Polyelectrolyte Adsorption to Glass and Cellulose Studied by Surface Force Technique

Interaction forces were measured between glass surfaces and between one glass and one cellulose surface in the presence of a 10% charged, random copolymer of acrylamide and cationic [3-(2-methylpropionamido)-propyl]trimethylammonium chloride (AM-MAPTAC-10), using a noninterferometric surface force technique (MASIF). Adsorption to glass from a 1 ppm solution leads to neutralization of the substrate negative surface charge. When the bulk polymer concentration is increased to 50 ppm, a weak charge reversal occurs as indicated by the reappearance of the double-layer force. Throughout the concentration range studied (1-50 ppm), the forces measured on approach between two glass surfaces could be adequately described by the DLVO theory. The interactions between one glass and one model cellulose surface under the same conditions follow a different pattern. AM-MAPTAC-10 adopts an extended conformation upon adsorption to cellulose and steric repulsion is generated when the thick adsorbed layer is compressed. The different structure of the adsorbed layers on cellulose is explained in terms of its lower surface charge density compared to glass. This leads to fewer attachment spots on the solid surface and an increased amount of polymer loops and tails proturding into solution; i.e., thicker adsorbed layers are formed and the resulting system is sterically stabilized.

13C NMR spectroscopy of cationic copolymers of acrylamide

Random copolymers of acrylamide and a quaternary ammonium acrylate monomer have been investigated by13C NMR spectroscopy in aqueous solution. Cleavage of the ester function has been shown to occur in mild alkaline media with a simultaneous intrachain reaction giving imide group formation. Sequential length distribution of the comonomers has been analyzed from triads composition and the experimental results lead to a nearly Bernouillian statistics although a more alternating distribution would be predicted from the reactivity ratios. This fact has been attribtued to the compositional heterogeneity of our copolymers which have been prepared at high degree of conversion.

Water‐soluble copolymers. IV. Random copolymers of acrylamide with sulfonated comonomers

AbstractRandom copolymers of acrylamide with sodium‐2‐sulfoethyl methacrylate and with sodium‐2‐acrylamido‐2‐methylpropane sulfonate were synthesized in aqueous solutions utilizing persulfate initiators. Copolymer compositions were determined by elemental analysis and by infrared spectroscopic methods. Monomer reactivity ratios were calculated using Fineman–Ross, Kelen–Tüdos, and/or Mayo–Lewis techniques at appropriate conversions. The copolymer microstructure, including mean sequence length distributions, was calculated from reactivity ratios. Membrane osmometry and viscometry measurements were utilized to estimate molecular weight and size. The large dimensions of these polyelectrolytes in aqueous solutions, as well as their inherent hydrogen bonding capacity and pseudoplasticity, make these copolymers excellent candidates for application as mobility control agents in enhanced oil recovery.

Block and graft copolymers: III. Apparent dissociation constants of copolymers of acrylic acid and acrylamide

The apparent dissociation constant of block, graft, and random copolymers of acrylamide and acrylic acid and of branched and linear polyacrylic acid has been measured by electrometric titrations in 0.1 N sodium chloride solution. Block copolymers have the same acid strength as linear homopolymers. Random copolymers are stronger acids than linear homopolymers, and graft and branched polymers are weaker acids. Reasons for the difference in apparent acid strength between branched and linear polyacrylic acids have been considered.